392 THE STELLAR UNIVERSE. 



number since then observed during the residence of that astronomer at the 

 cape of Good Hope. Although they are very irregularly scattered on the fir- 

 mament, there seems to be some ground for concluding that they prevail chiefly 

 in the direction of a great circle of the heavens inclined at a certain angle 

 with the general direction of the Milky Way. The following passages from 

 the memoirs of Sir William Herschel will better explain the manner in which 

 they are distributed than any mere general description which could be given : 



" The nebulae are arranged into strata, and run on to a great length ; and 

 some of them I have been able to pursue, and to guess pretty well at their 

 form and direction. It is probable enough that they may surround the whole 

 starry sphere of the heavens, not unlike the Milky Way, which undoubtedly 

 is nothing but a stratum of fixed stars. And as this latter immense starry bed 

 is not of equal breadth or lustre in every part, nor runs on in one straight di- 

 rection, but is curved and even divided into streams along a very considerable 

 portion of it, we may likewise expect the greatest variety in the strata of the 

 clusters of stars and nebulae. One of these nebulous beds is so rich, that in c 

 passing through a section of it, in the time of only thirty-six minutes, I have >' 

 detected no less than thirty-one nebulae all distinctly visible upon a fine blue 

 sky. Their situation and shape, as well as condition, seem to denote the 

 greatest variety imaginable. In another stratum, or perhaps a different branch 

 of the former, I have seen double and treble nebulae, variously arranged ; large 

 ones with small, seeming attendants ; narrow, but much-extended lucid nebulae 

 or bright dashes ; some of the shape of a fan, resembling an electric brush 

 issuing from a lucid point ; others of the cometic shape, with a seeming nu- 

 cleus in the centre, or like cloudy stars surrounded with a nebulous atmosphere. 

 A different sort, again, contain a nebulosity of the milky kind, like that won- 

 derful, inexplicable phenomenon about o Orionis ; while others shine with a 

 fainter mottled kind of light, which denotes their being resolvable into stars. 



" In my late observations on nebulae, I have found that I generally detected 

 them in certain directions rather than in others ; that the spaces preceding 

 them were generally quite deprived of their stars, so as often to afford many 

 fields without a single star in it ; that the nebulas generally appeared some 

 time after among stars of a certain considerable size, and but seldom among 

 very small stars ; and when I came to one nebula, I generally found several 

 more in the neighborhood ; that afterward a considerable time passed before I 

 came to another parcel. These events being often repeated in different alti- 

 tudes of my instrument, and some of them at considerable distances from each 

 other, it occurred to me that the intermediate spaces between the sweeps might 

 also contain nebulae ; and finding this to hold good more than once, I ventured 

 to give notice to my assistant at the clock that ' I found myself on nebulous 

 ground."' 



The conclusion, therefore, which follows from a general view of all the phe- 

 nomena is, that the sun is an individual star of one great cluster, occupy- 

 ing a position near to, but not in its centre ; that the stars of this cluster, seen 

 in every direction around us, constitute the starry heavens as they are visible 

 to us ; that those which are placed nearest to the sun in the cluster, present 

 to us the appearance of stars of the first magnitude, and that the others appear 

 to be less and less bright and large as their distances are greater and greater ; 

 that the most remote and most numerous stars of the cluster are individually 

 lost to the eye by their distance, but being confounded together like grains of 

 powder thickly sprinkled on the general firmament, form the Milky Way ; that 

 this cluster of ours is not the only one of the kind in the universe, but that 

 there are many thousands of others scattered through the depths of immensity ; 

 that those, which are nearest to our own cluster can be seen by sufficiently 



